69 340 problems

I'm starting to wonder if you accidently stopped at the diesel pump or jsut bought bad gas. I know you tryed to run off a gas jug before but maybe not long enough to get the bad out of the carb and now have bad fuel in the new carb.
You know you have spark if adjusting the timing effects how it turns over.
Fuel and spark are all thats needed. The quality of one or the other is your problem.
After 5 pages here and 200 plus spent there we should have found the fault by now.
I can't help but recall my uncle and his K car type Lebarron convertile (long time ago). He had it towed to the dealership 4 times and spent 3 times as much as you have. Electric fuel pump, fuel pump regulater, ECU. Problem was water in the gas the whole time.